In special relativity, when we say we are “observing” objects, we have to define precisely what we really mean by “observing”. On the one hand, “observing” can mean that we measure the length of a rod. This requires two individuals in the same frame of reference, with synchronized clocks. If these individuals see the two ends of the rod at the same time, they can determine the length of the rod from the difference of their coordinates, i.e., their distance. On the other hand, “observing” can also mean the way we are actually seeing an object. What we see of an object, at a definite moment in time, is what enters our eye, or a camera at that specific moment in time. Therefore, when and where the light started is irrelevant. What is important is that the light arrives simultaneously in our eyes, or the camera. In this chapter we shall concentrate on this second aspect of “seeing”, and study the visual appearance of fast moving objects in more detail. Furthermore, we shall have a look at how an observer traveling at relativistic velocities would perceive the starry sky.